You may simply fix the QBDBMgrN not running on this computer by installing Windows Firewall Updates. The instructions are provided to make doing so much simpler.
To begin, simultaneously press the Windows and R buttons on your keyboard.
Enter Control Panel in the Run box at this point.
The next action is to hit Enter and select System and Security.
The "firewall.cpl" command must then be used to access the firewall settings.
When finished, click Update your Firewall Settings in the Firewall Settings section, then select Firewall settings.
Now select the Use Suggested Options checkbox on the Update Now tab if Windows discovers any upgrades.
Moreover, you must wait till the installation procedure is finished.
Finally, restart your computer and launch QuickBooks once more to see if the error still occurs.

Reference - https://dataservicesolutions.com/blog/how-to-permanently-stop-qbdbmgrn-not-running-error/